In the past, a wafer with a laminated semiconductor layer was made into chips with a dicer, scriber, laser scriber, or the like.
However, a problem with a nitride semiconductor layer is that it is usually laminated on a wafer composed of a sapphire substrate, and a sapphire substrate does not tend to cleave parallel to an orientation flat (mainly the A face or C face), making it difficult to split the layer with a scriber or the like.
Also, when a nitride semiconductor layer is split with a dicer, a problem is that cracking, chipping, and the like are apt to occur when a mark is made with a grindstone.
Furthermore, when a groove is formed with a laser scriber and this groove is used for breaking, a split that is at an angle to the film thickness direction, that is, one that is inclined, may be made in the non-cleavable sapphire substrate, so that there is a split part of the way through the semiconductor layer that functions as an element, and this results in a defective product.
A method has been proposed to avoid such splitting, in which a first split groove is formed from the gallium nitride compound semiconductor layer side, a second split groove is formed from the sapphire substrate side at a location that does not overlap the center line of the first split groove, and chips are produced by effectively utilizing a split in an inclination direction (for example, Japanese Laid-Open Patent Application 2005-191551).
Another proposed method involves making chips by forming a first split groove in the surface of the semiconductor layer, and forming a second split groove by irradiating the interior of a sapphire substrate with a laser from the first split groove side (for example, Japanese Laid-Open Patent Application 2003-338468).
Yet another proposed method involves making chips by using a laser to internally work a sapphire substrate from the rear, and then scribing the rear of the sapphire substrate, or working the front by laser irradiation (for example, Japanese Laid-Open Patent Application 2005-109432).
Another proposed method involves establishing a predicted separation face in a predetermined inclination direction when directing a laser into the interior of a sapphire substrate, and directing the laser intermittently and in multiple stages from the rear face of the sapphire substrate so as to follow along this predicted separation face, and forcibly divide into chips in an inclination direction (for example, Japanese Laid-Open Patent Application 20006-245043).